Mechanical cotton pickers with spindle type picking units include drives synchronizing drum speed to ground speed. In the past, spindle and doffer speeds have been a direct ratio of the drum speed. To improve productivity the ground speed and therefore the drum speed have been increased. However, the maximum spindle and doffer speeds have remained generally constant. As a result the ratio of doffer and spindle speed to drum speed has to be reduced as well so that the maximum speeds are not exceeded when the harvester is operating at high ground speeds. The spindles therefore make fewer revolutions while engaging the row at any given speed and the doffers rotate more slowly. The reduced speed ratio of the spindles and doffers to the drum speed negatively impacts picking efficiency and conveying capacity, particularly in tough or high yielding cotton conditions.
Commonly assigned U.S. Pat. No. 5,325,656 illustrates several solutions for addressing the problems associated with spindle and doffer speeds. Solutions include an independent spindle drive system, a manual shift transmission to select different drive ratios, and an automatic transmission to provide two or more drive ratios. Although the independent drive and transmission systems help overcome the speed ratio problem, such systems can be costly. In addition, drive systems typically include multiple gear drives that can be very noisy and require a constant supply of grease. The row unit cabinet is manufactured with precision to assure proper gear meshing between the axes of the driven components.